维生素C在多壁碳纳米管/壳聚糖复合膜修饰玻碳电极上的电化学行为及测定

研究了维生素C在多壁碳纳米管/壳聚糖复合膜修饰玻碳电极上的电化学行为及测定。实验结果表明,在0.2 mol/L PBS(pH6.0)缓冲溶液中,修饰电极对抗坏血酸的氧化具有明显的催化和增敏效应,其氧化峰电位由 0.5 V负移至 0.1 V(vs.AgCl/Ag)。对修饰剂碳纳米管的用量、支持电解质、富集电位和富集时间等进行了优化。采用半微分伏安法进行定量测定,其线性范围为4.0×10-6~2.0×10-3mol/L,r=-0.998 3,检出限为1.0μmol/L。对抗坏血酸在修饰电极上的电化学行为进行了探讨,其电极反应为具有吸附特性和不可逆的电极过程,测得参加反应的质子数为2,电极反应的电子转移系数为0.59。测定了维生素C药片中抗坏血酸的含量,回收率在93%~105%。     

电化学活化玻碳电极吸附伏安法测定维生素K

维生素K类物质可在经电化学活化的玻碳电极上吸附富集并产生良好的伏安响应, 依此建立了吸附伏安法测定维生素K1和K3的方法. 在0.1 mol/L HCl的支持电解质中, 维生素K1在-0.025 V左右产生一对氧化还原峰, 其峰电流与浓度在1.1×10-6～2.2×10-5 mol/L范围内成良好的线性关系, 检出限为4.4×10-7 mol/L; 维生素K3则在+0.059 V左右产生一对氧化还原峰, 其线性范围为1.8×10-7～3.0×10-5 mol/L, 检出限为9.1×10-8 mol/L. 该方法可用于测定药品中的维生素K1和K3.     

氟嗪酸在碳纳米管修饰电极上的电化学行为及含量的测定

在玻碳电极上制备了多壁碳纳米管/Nafion(MWNTs-Nafion)膜,用交流阻抗谱(EIS)、循环伏安法(CV)、线性扫描伏安法(LSV)研究了氟嗪酸在该膜上的电化学行为。与裸玻碳电极相比,这种纳米结构膜修饰的电极对氟嗪酸的电化学氧化显现出极好的促进作用,氟嗪酸的氧化峰电流明显增强,在修饰电极上于 0.97 V处产生了1个灵敏氧化峰。LSV测定氟嗪酸的线性范围为1.0×10-8～1.0×10-6mol/L和1.0×10-6～2.0×10-5mol/L,开路富集400 s后,检出限为8.0×10-9mol/L(3倍信噪比),方法可用于人尿中氟嗪酸的实时测定。     

聚吡咯／多壁碳纳米管修饰电极对多巴胺的测定

制备了聚吡咯/多壁碳纳米管(PPy/MWNT)复合膜修饰电极。研究了神经递质多巴胺(DA)在该修饰电极上的电化学行为。实验表明,PPy/MWNT复合膜修饰电极对DA的电催化作用优于PPy修饰电极。在pH=4.10的0.2mol/L醋酸-醋酸钠缓冲溶液中,DA在该修饰电极上的CV曲线于0.31V和0.28V处出现一对灵敏的氧化还原峰,峰电位差△Ep比裸玻碳电极降低58mV,比PPy修饰电极降低28mV,峰电流显著增加。氧化峰电流ipa与DA浓度在1.0×10-4~7.8×10-8mol/L范围内呈良好的线性关系,线性回归方程为ip(μA)=0.2512 1.2300C(×10-5mol/L),相关系数r=0.9992,检出限为3.9×10-8mol/L。常见物质对DA的检测无干扰,DA注射液样品检测回收率为94%~104%。     

羧基化单壁碳纳米管-纳米金复合膜修饰电极测定己烯雌酚

通过自组装技术,制备了羧基化单壁碳纳米管-纳米金复合膜修饰玻碳电极,己烯雌酚在该修饰电极上有良好的电化学行为,于0.20V和0.135V分别出现一氧化还原峰,考察了pH、扫描速度、富集电压、富集时间等对峰电流的影响。利用差分脉冲伏安法,氧化峰峰电流与DES浓度在2.0×10~(-9)~3.0×10~(-7)mol/L范围内呈良好的线性关系,检出限为9.0×10~(-10)mol/L。方法可用于药片中己烯雌酚含量的测定。     

碳纳米管修饰电极上沙丁胺醇电催化氧化研究

将多壁碳纳米管(MWNT)分散在疏水性表面活性剂双十六烷基磷酸(DHP)溶液中形成稳定、均相的分散液,然后制备多壁碳纳米管-DHP复合膜修饰玻碳电极(MWNT-DHP/GCE).应用方波伏安法研究了沙丁胺醇在修饰电极上的电化学行为,结果表明,碳纳米管复合膜修饰电极对沙丁胺醇的氧化有良好的电催化活性,其氧化反应为一电子一质子过程,氧化电位比裸玻碳电极负移40 mV,峰电流增加了4.5倍.在最佳测试条件下,氧化峰电流与沙丁胺醇浓度在8.3×10-7~3.3×10-6mol/L范围内呈良好线性关系,开路富集2min,检出限达1.8×10-7mol/L.该修饰电极具有良好的重现性、稳定性.     

双酚A在壳聚糖石墨烯复合膜电化学传感器上的电化学行为及测定

采用hummers法制备了石墨烯,以碳糊电极为基底电极采用滴涂法制备了壳聚糖石墨烯复合膜电化学传感器(CTS/GR/CPE),并利用循环伏安法和线性扫描溶出伏安法研究了双酚A在电化学传感器上的电化学行为。在pH 7.4的磷酸盐缓冲液中,于-0.1V富集180s后,该电化学传感器对双酚A具有良好的电催化作用,于0.564V处有一灵敏的氧化峰,线性范围为1.00×10-6～7.00×10-5mol/L和7.00×10-5～1.00×10-3mol/L,检出限(S/N=3)为1.00×10-7mol/L。方法用于塑料制品中溶出双酚A的测定,回收率为96.4%～100.5%。     

羧基化碳纳米管修饰碳糊电极伏安法测定食盐中碘酸根

应用羧基化多壁碳纳米管(c-MWCNT)修饰碳糊电极,测定食盐中的碘酸根含量.在0.1 mol/L的NaOH电解液中,当IO3-在羧基化多壁碳纳米管修饰碳糊电极表面富集60 s,电位扫速为300 mV/s时,该修饰电极在线性扫描伏安图上能出现一灵敏的阴极溶出峰,峰电位为-0.52 V,峰电流与IO3-浓度在8.0×10-10~5.0×10-8mol/L和1.0×10-7~3.0×10-6mol/L的范围内成良好线关系,相关系数分别为0.999和0.998,检出限可达1.0×10-11mol/L;该修饰电极无汞,稳定性较好,用于加碘食盐中碘酸根含量的测定灵敏度高,平均回收率为101.1%.循环伏安(CV)测试表明,碘酸根在修饰电极上电化学反应是一不可逆过程,其电极反应标准均相速率常数为0.0109 cm.s-1.     

吡硫醇在单壁碳纳米管修饰电极上电化学行为的研究

研究了吡硫醇在单壁碳纳米管修饰电极上的电化学行为,提出了一种检测吡硫醇的电化学方法.在0.1 mol/L的NaAc-HAc(pH 4.0)缓冲溶液中,吡硫醇在单壁碳纳米管修饰电极上出现一灵敏的氧化峰,峰电位位于0094 V处.与裸玻碳电极相比,单壁碳纳米管修饰电极显著提高了吡硫醇的氧化峰电流.在最佳实验条件下,吡硫醇浓度在9.9×10~(-6)～5.7×10~(-4) mol/L范围内与峰电流呈良好的线性关系,检出限为2.98×10~(-7) mol/L.吡硫醇在单壁碳纳米管修饰电极上的氧化过程受吸附控制,为1电子2质子的过程.     

聚苏木精修饰玻碳电极测定酪氨酸

通过在玻碳电极上电聚合聚苏木精的方法制备了聚苏木精修饰电极,研究了酪氨酸在修饰电极上的电化学行为。在0.1 mol/L磷酸盐缓冲溶液(pH3.0)中,富集电位为-0.3 V,富集时间为180 s,氧化峰电流与酪氨酸的浓度在5.0×10-6～1.0×10-4mol/L的范围内呈良好的线性关系,检出限为3.0×10-7mo...     

Ni/ZSM‐5 Zeolite Modified Carbon Paste Electrode as an Efficient Electrode for Electrocatalytic Oxidation of Formaldehyde

In this study, we prepared a modified carbon paste electrode consisting of Nickel entrapped in synthesized ZSM‐5 zeolite (Ni/ZMCPE). Then Ni(II) ions were incorporated to electrode by immersion of modified electrode in 1 M Ni(II) ion solution. Cyclic voltammetry and chronoamperometry experiments were used for electrochemical study of this modified electrode; a good redox behavior of Ni(OH)₂/NiOOH couple at the surface of electrode can be observed, the excellent capability of this modified electrode for catalytic oxidation of formaldehyde was demonstrated during the anodic potential sweep in alkaline solution. The amount of transfer coefficient (α), surface coverage (Γ*) of the redox species and catalytic chemical reaction rate constant (k) for formaldehyde were evaluated. Thus, it can be a candidate as an anode for fuel cell application.     

Voltammetric sensing of paracetamol, dopamine and 4-aminophenol at a glassy carbon electrode coated with gold nanoparticles and an organophillic layered double hydroxide

A differential pulse voltammetric method was developed for the simultaneous determination of paracetamol, 4-aminophenol and dopamine at pH 7.0 using a glassy carbon electrode (GCE) coated with gold nanoparticles (AuNPs) and a layered double hydroxide sodium modified with dodecyl sulfate (SDS-LDH). The modified electrode displays excellent redox activity towards paracetamol, and the redox current is increased (and the corresponding over-potential decreased) compared to those of the bare GCE, the AuNPs-modified GCE, and the SDS-LDH-modified GCE. The modified electrode enables the determination of paracetamol in the concentration range from 0.5 to 400???M, with a detection limit of 0.13???M (at an S/N of 3). The sensor was successfully applied to the stimultaneous determination of paracetamol and dopamine, and of paracetamol and 4-aminophenol, respectively, in pharmaceutical tablets and in spiked human serum samples.

Electrocatalytic Oxidation of Folic Acid on Carbon Paste Electrode Modified by Nickel Ions Dispersed into Poly(o‐anisidine) Film

Poly(o‐anisidine) (POA) was formed by successive cyclic voltammetry in monomer solution containing sodium dodecyl sulfate (SDS) at the surface of carbon paste electrode. Then Ni(II) ions were incorporated to electrode by immersion of the polymeric modified electrode having amine group in 0.1 M Ni(II) ion solution. Cyclic voltammetric and chronoamperometric experiments were used for the electrochemical study of this modified electrode; a good redox behavior of Ni(OH)₂/NiOOH couple at the surface of electrode can be observed. The capability of this modified electrode for catalytic oxidation of folic acid was demonstrated. The amount of α and surface coverage (Γ*) of the redox species and catalytic chemical reaction rate constant (k) for folic acid oxidation were calculated. The catalytic oxidation peak current of folic acid was linearly dependent on its concentration and a linear calibration curve was obtained in the range of 0.1 to 5 mM with a correlation coefficient of 0.9994. The limit of detection (3σ) was determined as 0.091 mM. This electrocatalytic oxidation was used as simple, selective and precise voltammetric method for determination of folic acid in pharmaceutical preparations.     

Direct Electrical Wiring of Oxidoreductase Enzymes to Silicate Based Electrodes

Three types of reagentless glucose biosensor based on composite graphite-ormosil materials are described: (1) a redox modified silicate-graphite electrode doped with glucose oxidase, (2) a methyl silicate-graphite material doped with redox modified glucose oxidase, and (3) a methyl silicate and redox modified graphite composite material doped with glucose oxidase.     

Application of a palladium hexacyanoferrate film-modified aluminum electrode to electrocatalytic oxidation of hydrazine.

A palladium hexacyanoferrate (PdHCF) film as an electrocatalytic material was obtained at an aluminum (Al) electrode by a simple electroless dipping method. The modified Al electrode demonstrated a well-behaved redox couple due to the redox reaction of the PdHCF film. The PdHCF film showed an excellent electrocatalytic activity toward the oxidation of hydrazine. The electrocatalytic oxidation of hydrazine was studied by cyclic voltammetry and rotating disk electrode voltammetry techniques. A calibration graph obtained for the hydrazine consisted of two segments (localized at concentration ranges 0.39-10 and 20-75 mM). The rate constant k and transfer coefficient alpha for the catalytic reaction and the diffusion coefficient of hydrazine in the solution D, were found to be 3.11 x 10(3) M(-1) s(-1), 0.52 and 8.03 x 10(-6) cm2 s(-1) respectively. The modified electrode was used to amperometric determination of hydrazine in photographic developer. The interference of ascorbic acid and thiosulfate were investigated and greatly reduced using a thin film of Nafion on the modified electrode. The modified electrode indicated reproducible behavior and a high level of stability during electrochemical experiments, making it particularly suitable for analytical purposes.     

离子液体-Ni微/纳米粒子协同电催化检测维生素B2

本文制备了离子液体-Ni微/纳米粒子修饰碳糊电极.研究了离子液体对Ni微/纳米粒子氧化还原的促进作用,用循环伏安法在0.1 mol/L B-R缓冲溶液(pH=4.5)中研究了维生素B2(VB2)在该修饰电极上的电化学行为,优化了各种实验条件.实验结果表明,本文制备的修饰电极能很好地催化氧化VB2,VB2在该修饰电极上的...     

Voltammetric Characterization of Grafted Polymer Modified with ZnO Nanoparticles on Glassy Carbon Electrode

In this study, a grafted polymer (GP) with ZnO nanoparticles (GP/ZnO NPs) was attached on the surface of glassy carbon electrode (GCE), in order to produce a new modified electrode (GP/ZnO NPs-GCE). The gamma irradiation method was used to grafted polystyrene (polymer) with acrylonitrile (monomer), while slow evaporation process was used to prepare the new modified electrode. The cyclic voltammetry (CV) of K₄[Fe(CN)₆] was used to study the electrochemical properties GP/ZnO NPs-GCE. The peak separation (ΔE_pa-c) was 500 mV between the redox peaks of Fe(II)/Fe(III) in an aqueous solution of 1 M KCl and the current ratio of redox current peaks (I_pa/I_pc) was ≈ 1 for the modified electrode. This indicated that the modified electrode has s good reversibility and conductivity, wherefore; it was applied in the voltammetric filed. It was found that the modified electrode GP/ZnO NPs-GCE have a reasonable solubility and stability at various pH medium. Additionally, the sensitivity of the electrochemical analysis by cyclic voltammetric (CV) method is extensively subjected to the pH medium and the scan rate (SR). A couple of redox current peaks of K₄[Fe(CN)₆] in KCl solution was observed with a reversible process: Fe³⁺/Fe²⁺. Finally a good diffusion coefficient of electroactive species (D) for the new modified electrode was found in this study by chronoamperometry method using Cottrell equation.     

以乙二胺为手臂分子制备的DNA修饰电极及其伏安性能

Carboxyl was formed on the surface of glassy carbon electrode(GCE) by electrochemical oxidation. Ethylenediamine(En) was used as the arm molecule to link carboxyl with dsDNA using 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC) and N- hydroxysuccinimide (NHS) as the activators to prepare dsDNA modified electrode(dsDNA/En/GCE). It was shown that dsDNA couM be covalently immobilized on the surface of GCE. ssDNA modified electrode(ssDNA/En/GCE) was obtained via the thermal denaturation of dsDNA/En/GCE. The dsDNA/En/GCE and ssDNA/En/GCE were characterized by voltammetry with methylene blue(MB) as the indicator. The results indicated that the currents of the redox peaks of MB at ssDNA/En/GCE were larger than those at dsDNA/En/GCE, and the currents of the redox peaks at En/GCE were the smallest. The peak-currents of MB at the DNA modified electrode had good reproducibility after multi-denaturation and hybridization cycles.     

Characterization and application of an electrode modified by mechanically immobilized copper hexacyanoferrate

A newly modified electrode was prepared by mechanical immobilization of copper hexacyanoferrate (CuHCF) on a graphite electrode. The modified electrode was characterized by cyclic voltammetric experiments. The effect of different background electrolytes, pHs and scan rates on the electrochemical behaviour of the electrode has been evaluated. In NH₄Cl two reversible redox peaks were observed. The first redox peak corresponding to Cu⁺/Cu²⁺ is observed only in this medium. The second redox peak corresponds to the Fe(CN)₆ ^4–/Fe(CN)₆ ^3– couple. Both anodic peaks were used for catalytic oxidation of ascorbic acid. As the anodic current for catalytic oxidation was proportional to the amount of ascorbic acid, an analytical method was developed for the determination of ascorbic acid in commercial samples.     

Electrocatalytic Oxidation of Some Carbohydrates by Nickel/Poly(o‐Aminophenol) Modified Carbon Paste Electrode

This study investigates the electrocatalytic oxidation of glucose and some other carbohydrates on nickel/poly(o‐aminophenol) modified carbon paste electrode as an enzyme free electrode in alkaline solution. Poly(o‐aminophenol) was prepared by electropolymerization using a carbon paste electrode bulk modified with o‐aminophenol and continuous cyclic voltammetry in HClO₄ solution. Then Ni(II) ions were incorporated to electrode by immersion of the polymeric modified electrode having amine group in 1 M Ni(II) ion solution. Cyclic voltammetric and chronoamperometric experiments were used for the electrochemical study of this modified electrode; a good redox behavior of Ni(OH)₂/NiOOH couple at the surface of electrode can be observed, the capability of this modified electrode for catalytic oxidation of glucose and other carbohydrates was demonstrated. The amount of α and surface coverage (Γ*) of the redox species and catalytic chemical reaction rate constant (k) for each carbohydrate were calculated. Also, the electrocatalytic oxidation peak currents of all tested carbohydrates exhibit a good linear dependence on concentration and their quantification can be done easily.